Three-dimensional WO3 nanorod arrays on Si as photoanodes for efficient photoelectrochemical water splitting

Abstract

Arrays of WO3–Si forest hierarchical structures have been successfully synthesized by growing WO3 nanorod on the surface of vertically aligned n-Si micropillar arrays using a chemical vapor deposition technique. The three-dimensional (3D) WO3–Si nanorod forest improves photoelectrochemical performances; it exhibits higher photocurrent density and a more negative onset potential of 0.5 V vs. reversible hydrogen electrode compared with the WO3 nanorod array on planar Si substrate. More importantly, this directly grown 3D hierarchical structure exhibits extraordinary stability for water oxidation with negligible losses of photoactivity for 24 h in a neutral pH solution. The enhanced photostability is attributed not only to the formation of O vacancies in WO3, which is resistive to photocorrosion but also the multiple internal reflection in 3D hierarchical structure. Our work demonstrates the importance of structural innovation in improving solar water efficiency.